In this chapter, we reconsider the key lessons presented by more than two decades of empirical research on international knowledge flows. We begin by reviewing some of the key empirical findings and policy lessons from that literature. We then build on this review by pointing out the importance and uneven distribution across developing countries of absorptive capacity, which may help explain the uneven diffusion of knowledge across these countries. We also consider the implications of growing R&D globalization, the potentially declining importance of international manufacturing value chains, the rise of global trade in services, and the new opportunities opened up by AI-enhanced learning technologies.